A casus belli, sometimes abbreviated CB and meaning "cause for war" in Latin, represents a justification for war that is recognized as legitimate by other characters. A ruler must have a valid casus belli in order to be able to declare war upon another ruler and can only gain from a war what the casus belli specifies.
War target[edit | edit source]
The war target is the map region which is targeted by a casus belli. If the casus belli does not target a map region then the defender's realm capital becomes the war target.
The attacking side gains more war score by occupying holdings located in the war target region. After a grace period, the defender will passively gain war score by holding all counties in the war target region.
CB list[edit | edit source]
Each casus belli will cost prestige and/or piety. If the attacker can't pay the cost, it can pay with a level of fame or devotion instead. Declaring war against a character's head of faith costs 500 piety if the head of faith is spiritual and 100 piety if they are temporal. Declaring war against a theocracy of the same faith additionally costs 100 piety, stacking with the cost for attacking the head of faith.
Casus belli costs can be removed via one of the game rules.
|Casus belli||Requirements||Cost||Enforce Demands effect||White Peace effect||Surrender effect|
|Independence War||Target is the liege||
|Subjugate?|| One of the following:
|Artifact Claim War||Claim on one of the target's artifacts||150 prestige||
|Raid for Captives||Faith has the Human Sacrifice tenet||
|Ducal Conquest of County||
||125 prestige per county||
|Laudably Conquer County||
|Mongol Invasion of Kingdom||
|Restore Imperial Province||None||
Claims CB[edit | edit source]
The Claims casus belli can only be used against characters holding a title either you or one of your vassals, courtiers or guests has a claim on. Initially only one claimed title can be selected but multiple titles can be chosen with the Divine Right innovation for personal claims and Rightful Ownership innovation for vassal or courtier claims.
- If the war ends by enforcing demands, the claimant will gain the target titles. If they're a vassal, courtier or guest, their liege will gain a weak hook on them.
- If the war ends by white peace, the defender keeps the target titles.
- If the war ends by surrender, the defender keeps the target title and the claims used for the casus belli are lost.
Declaring war over claims requires the following amount of Prestige:
|Rank||Own claim||Other's claim|
De jure CBs[edit | edit source]
Where a title belongs to another title de jure (a county to a duchy, duchy to a Kingdom etc.), the holder of the higher title has a de jure CB towards the character who holds the lower title if they're not already a vassal. All de jure CBs cost 100 prestige per county in the war target title and have a war contribution share of 300 prestige.
- If the war ends by enforcing demands, the attacker will gain the target title. If they're a vassal, their liege will gain a weak hook on them.
- If the war ends by white peace, the defender keeps the target title.
- If the war ends by surrender, the defender keeps the target title and the attacker pays gold to the defender.
|Casus belli||War target rank||Required innovation|
|Seize De Jure County||County||Casus Belli|
|Seize De Jure Duchy||Duchy||Chronicle Writing|
|Seize All De Jure Lands||All titles||Rightful Ownership|
Conquest and Invasion CBs[edit | edit source]
The following CBs are only available to rulers who have clan or tribal government or whose faith has the Warmonger or Pursuit of Power tenets.
- If the war ends by enforcing demands, the attacker will gain the target title and fame equal to the war contribution share.
- If the war ends by white peace, the defender keeps the target title and the attacker loses 75-100 prestige.
- If the war ends by surrender, the defender keeps the target title, while the attacker pays the defender gold and gains +25 faction discontent.
Gains titles held personally by target in the duchy or kingdom, or if the county holders have land elsewhere, vassals who only own land in the target will transfer to you in duchy and kingdom wars. As an empire you can vassalize a ruler with many kingdom titles in an invasion war, with the king keeping everything outside the target kingdom as your new vassal.
Holy war CBs[edit | edit source]
The following CBs will cause a holy war instead of a regular one. This requires the Faith to be organized and to not have a tenet that forbids holy wars, such as Pacifism or Dharmic Pacifism. In any case, it can only target a ruler whose faith is considered Hostile or Evil.
- If the war ends by enforcing demands, the attacker will gain all titles held by rulers of Hostile or Evil faith and vassalize all other rulers in the war target region. The defender gains twice the fervor the attacker paid.
- If the war ends by white peace, the defender keeps all their titles and the attacker loses 50 piety.
- If the war ends by surrender, the defender keeps all their titles, while the attacker pays gold and gains +25 faction discontent and −15 vassal opinion for 5 years.
Migrate to Pannonia[edit | edit source]
Migrate to Pannonia is a unique casus belli with special mechanics that can only be used once per game by characters of Táltosist faith who make the Prepare to Cross the Carpathians decision against characters in the Pannonian Basin region. If the Hungarian Migration game rule is set to Immediate, the game will start with the casus belli being used by Grand Prince Álmos Ügyekfi of the Mogyër Confederation against King Boris of Bulgaria.
If the war ends in white peace, the defender keeps his or her titles. If it ends in surrender the attacker's factions will also gain discontent. If the war ends by enforcing demands however it will have the following effects:
- Attacker gains all titles held by the defender in the Pannonian Basin region.
- Attacker gains the Kingdom of Hungary title, which replaces Kingdom of Pannonia.
- Any other kingdom title held by the attacker is destroyed.
- All held titles that are not within the de jure Kingdom of Hungary are given to new randomly generated characters of their culture and religion.
- All vassals that are not within the de jure Kingdom of Hungary become independent.
- All controlled counties convert to Mogyër culture and Táltosist faith.
- All previously controlled counties convert to Pecheneg culture.
When war is declared with this casus belli, the following army will be spawned, which will persist for as long as the attacking character lives or until destroyed or disbanded:
Varangian Adventure[edit | edit source]
Varangian Adventure is a unique casus belli with special mechanics that can only be used during the Tribal Era on counties and duchies owned by characters from a different culture group. It costs 1000 prestige. To be used it requires the Varangian Adventurers innovation, which is only available to Estonian and Norse cultures and requires the Northern Lords DLC. It can be used multiple times but each use will cost more than the previous one. It cannot be used by kings or emperors or if there's another ongoing war.
If the war ends in white peace, the defender keeps his or her titles. If it ends in surrender, the attacker must also pay gold and prestige to the defender. If the war ends by enforcing demands however it will have the following effects:
- All titles held by the attacker are destroyed or given to other characters.
- All vassals are given independence.
- Attacker gains the target title and all titles that are de jure part of it.
- Attacker gains the Adventurer trait.
- Attacker gains 200 gold.
- If the target title was a county and its de jure duchy does not exist or is part of the defender's realm, the duchy is given to the attacker.
- If the target title was feudal, the attacker's Government changes to Feudal.
When war is declared using this casus belli for the first time, it will spawn for the duration of the war the following army based on the number of owned counties of the same faith and culture in the region of Mainland Scandinavia:
AI rulers will only use this casus belli if all their held titles are located in the Mainland Scandinavia region. If the Scandinavian Adventurers game rule is not set to Apocalyptic then they also require the Ambitious trait, as well as at least two of the following traits: Adventurer, Arrogant, Brave, Greedy.
Notes[edit | edit source]
- The maximum size is a base of 3 counties, plus 2 counties for each of the following innovations that the attacker's culture has: Casus Belli, Chronicle Writing, Divine Right, and Rightful Ownership.